1. Field of the Invention
This invention relates to an image forming apparatus such as a copying-machine, a facsimile machine, a printer, and a compound machine having combined functions of these machines.
2. Description of the Background Art
There has been known a certain type of image forming apparatus with a frame structure comprising a main base frame internally provided with an imaging unit including a photoreceptor, and an upper frame vertically and pivotally openable about an axis of a pivot provided on one end thereof (e.g., on the rear side of the apparatus) to open the opposite side (e.g., the front side of the apparatus). The upper frame has an operation unit arranged with ten keys, a start key, etc. The apparatus further comprises a document feeder unit mounted on the upper frame to automatically feed original documents successively.
The document feeder unit comprises a housing member directly mounted on the upper frame, a guide member linked to the rear side of the housing member (i.e., rear side of the apparatus) to be pivotable relative to the housing member, and a document feed roller mounted on the housing member and the guide member.
The above conventional apparatus is constructed such that a document insertion tray is provided on the front side of the housing member, while a document discharge tray is provided on the rear side of the housing member. A recording paper insertion tray is provided on the rear side of the housing member, underneath the document discharge tray to set a stack of recording paper and transport the same inside the main base frame. A recording paper discharge tray is provided on the front side of the main base frame, e.g., beneath the document insertion tray for receiving the recording paper with the image recorded by the imaging unit to discharge the same outside the main base frame.
In the image forming apparatus having the above arrangement, original documents set on the document insertion tray are fed one by one to a document reader unit including a contact type image sensor to have the image of each document read line after line. Each time the entire image of one original document is read by the document reader unit, the document is discharged onto the document discharge tray, thereby discharging the documents one after another.
In the meantime, a sheet of recording paper stacked on the recording paper insertion tray is transported inside the main base frame in synchronism with the above image reading operation by the document reader unit, and is discharged onto the recording paper discharge tray after the image recording by the imaging unit. In case where the recording paper is brought to a jammed state during the transport, an operator pivotally opens up the upper frame to make an opening on the upper front side of the apparatus, and removes the jammed recording paper through the opening.
The above conventional image forming apparatus has the following drawback. Since the document insertion tray is mounted on the frontal end of the housing member constituting the document feeder unit, the document insertion tray also pivotally moves together with the housing member that is directly mounted on the upper frame in opening up the upper frame.
Hence, the radius of locus defined by the pivotal movement of the upper frame becomes extensively large because the radius of locus is made up not only with the length of the upper frame also with the length of the tray extending from the frontal end of the upper frame i.e., a length from the pivotal shaft to the radial outermost end of the tray. This results in an inconvenience in opening and closing the upper frame.
The apparatus can take an arrangement other than the above in which the document insertion tray and the document discharge tray are mounted in the opposite way, i.e., the document insertion tray is mounted on the rear side of the housing member, and the document discharge tray is mounted on the frontal end of the housing member. However, this arrangement also cannot avoid an extended radius of the upper frame when the upper frame pivotally moves, since the document discharge tray also pivotally moves together with the upper frame.